Coastal regions play a crucial role for greenhouse gases (GHG) budgets since biological cycling and sediment-water-air exchanges are more intense than in open ocean settings. Since coastal ecosystems already experience seasonal hypoxia, ongoing deoxygenation is of concern as it could exacerbate GHG-driven global warming, negatively affecting several biological communities. Lake Grevelingen is a saline coastal reservoir with seasonally hypoxic conditions resulting from limited water exchange after two dams were built in the 60s–70s. As such, it offers an excellent opportunity to elucidate the role of oxygen temporal-spatial variability on GHG dynamics. N₂O stands out among other GHG because of its contribution to stratospheric ozone depletion and its effectiveness in enhancing Earth’s warming. Given the tight coupling of N₂O production and low oxygen concentrations, coastal margins are expected to be high sources to the atmosphere. However, emission estimates in these areas are highly uncertain and mechanistic understanding on the benthic-pelagic coupling of N₂O fluxes and its potential changes with deoxygenation is still rudimentary. In this presentation, we show the first results of an extensive campaign which combines novel benthic profiling, high-resolution water column and surface water measurements, and floating chamber experiments. We discuss the spatial and temporal variability of N₂O fluxes across the sediment-water-air interfaces in the lake and present a budget which could be used to improve the representation of coastal fluxes in ocean models.  

Primary Presenter: Damian Arévalo-Martínez, Radboud University Nijmegen (d.arevalomartinez@science.ru.nl)

Authors:

Damian L. Arévalo-Martínez, Radboud University Nijmegen  (d.arevalomartinez@science.ru.nl)

Marit R. van Erk, Utrecht University  (m.r.vanerk@uu.nl)

Hermann W. Bange, GEOMAR Helmholtz Centre for Ocean Research Kiel  (hbange@geomar.de)

Niels A.G.M. van Helmond, Radboud University Nijmegen / Utrecht University  (niels.vanhelmond@ru.nl)

Wytze K. Lenstra, Radboud University Nijmegen / Utrecht University  (W.K.Lenstra@uu.nl)

Sarah Schrammeck, Radboud University Nijmegen  (sarah.schrammeck@ru.nl)

Olga Zygadlowska, Utrecht University  (o.m.zygadlowska@uu.nl)

Mike M.S.M. Jetten, Radboud University Nijmegen  (mike.jetten@ru.nl)

Caroline P. Slomp, Radboud University Nijmegen / Utrecht University  (caroline.slomp@ru.nl)